Good morning,

I was wondering how you conduct a proper compression test on the Z. I have a "peak-hold" compression guage and the necessary fittings. I also know the general idea (pull plug, hook-up gauage, turn over engine). However, I don't know the exact steps for a good test. For example, what should I disconnect to keep the engine from firing up? I assume I disconnect the plug wires/coilpacks, but I am not sure. Also, if I do disconnect the plug wires/coilpacks, how do I keep from getting shocked, blowing a fuse, or causing other problems.

Any help would be great. Thanks.

 

First off, you should generally do it with a warm engine otherwise your readings will more than likely be low. Get some gloves, because the spark plugs will be hot. Then pull fuse #81, fuel pump fuse. Let engine idle until it dies then try to start again until your sure there's no fuel pressure left.

Remove all coil pack and spark plugs. Disconnect coil pack connectors.(this will disable your ignition system). Cover the spark plug holes with clean rags so no dirt or debris gets in them. Put gauge in cylinders to be tested. Turn over engine about 5 seconds each. If there are any cylinder pressures that are low, squirt a little engine oil in the cylinder, if pressure is higher after oil is squirted in, this would indicate worn rings.

 

Jesse, as always, you are the man. Thanks.

 

No problem. Forgot to mention something. If a cylinder is reading low pressure and the squirting oil trick doesn't raise the pressure, then you're looking at a valve problem.

Any particular reason you're doing a compression check?

 

or a bent rod... BTW each Cyinder should be at 120

 

According to the FSM the reading should be 185PSI, minimum of 142PSI. There should be no more than 14 PSI difference between the highest and lowest cylinder.

Oh, while reading through the FSM compression test procedures, they also mention that if two or more cylinders are low and the oil squirt thing doesn't work then you could have a head gasket problem.

 

I think you forgot to mention that while you are doing the compression test, you have to be W.O.T. otherwise you will end with 15 lbs lower than the correct cylinder compression.

 

Yeah, oops sorry.